when you do exercises training an agonist muscle like biceps, isn't the antagonist (triceps) making a resistance power qual to the agonist force, and by this the antagonist is trained also equal to the agonist, it is said that the antagonist needs training separately, i don't understand this process well so i need an explanation please ?

No, the antagonist muscle does not generate equal force - if it did, muscles could not cause movement. Thus, you also need to train both the agonist and antagonist separately.

The antagonist generates some force, though - the amount depending on the situation. This stabilizes the joint and also prevents you from exceeding the natural range of motion of the joint and damaging the joint and/or ligaments.

In some cases of isometric muscle work (the muscle length does not change), for example when you try to firmly fix your arm into certain position without external force affecting your arm, both the agonist and antagonist may create similar force. But this is not really an optimal way to train the muscle. However, isometric work with a direction of force can be used effectively in muscle training (the human flag exercise, for example, with gravity pulling your body weight down :)

No, the antagonist muscle does not generate equal force - if it did, muscles could not cause movement. Thus, you also need to train both the agonist and antagonist separately.

The antagonist generates some force, though - the amount depending on the situation. This stabilizes the joint and also prevents you from exceeding the natural range of motion of the joint and damaging the joint and/or ligaments.

In some cases of isometric muscle work (the muscle length does not change), for example when you try to firmly fix your arm into certain position without external force affecting your arm, both the agonist and antagonist may create similar force. But this is not really an optimal way to train the muscle. However, isometric work with a direction of force can be used effectively in muscle training (the human flag exercise, for example, with gravity pulling your body weight down